Red Sea disease kills sea urchins, threatened corals

By Hannah Confino and Ari Rabinovitch

TEL AVIV (Reuters) – A deadly disease spreading through the Red Sea has killed entire species of sea urchins in the Gulf of Aqaba, endangering the region’s uniquely resilient coral reefs, a group said. Israeli research has discovered.

According to a team from Tel Aviv University, entire populations of black sea urchins, a species known for helping to keep coral reefs healthy in the waters also known as Eilat Bay, have been wiped out in the past year. months.

Their findings, published in two peer-reviewed journals, cite mass mortality rates in other countries in the region, including Jordan, Egypt and Saudi Arabia.

The probable culprit is a rapidly fatal disease-causing cilia parasite – perhaps the same kind that devastated the Caribbean sea urchin population.

In just two days, a healthy Diadema setosum – a species of black sea urchin with long spines – becomes a skeleton with large tissue loss, said lead researcher Omri Bronstein, from the Steinhardt Museum of Natural History and School of Animals. from Tel Aviv University said.

Some washed ashore and died. Others are eaten by fish, potentially speeding up the spread.

The first signs of trouble appeared in the Mediterranean Sea, where sea urchins have colonized over the years, possibly through the Suez Canal, and made their home. Bronstein said a few months ago there were reports from Greece and Türkiye of sea urchin deaths.

While that was of little concern at first because they were an invasive species, the pathogen has now returned to natural populations in the Red Sea.

“There’s nothing that can be done to prevent this at the moment,” Bronstein said.

But there is a “very narrow window,” he said, to create an isolated population, or parent colony, of sea urchins left in other places that could hopefully be reintroduced later. .

A report has been submitted to Israel’s environmental agencies and urgent steps to protect coral reefs are under consideration, the researchers said.

Eilat, an Israeli resort town on the northern coast of the Red Sea, is a popular spot for scuba diving. Scientists studying the area consider it a refuge for corals.

Corals that settled thousands of years ago must pass through a narrow strait to the south that acts as a heat barrier, ensuring they are resistant to the temperature rise that is threatening coral reefs globally.

Sea urchins play an important role in maintaining balance by eating algae that would otherwise block sunlight and suffocate coral reefs.

“Corals don’t have a chance to compete with algae. That’s why we need sea urchins,” he said. “Without this species, as we have seen – this is not imagination, we have seen it happen right before our eyes – it is not a good future.”